The invention relates to the determination of port identities in a telecommunications system and, in particular to the automatic determination of port identities in a heterogenous telecommunications system.
In 1876, inside a third floor walk-up garret apartment in the Scollay Square section of Boston Mass., Alexander Graham Bell spoke the first sentence transmitted over telephone wires. Technical innovations have dramatically transformed the telecommunications industry over the past one hundred and twenty three years. For example, telecommunications switching systems have evolved considerably from xe2x80x9chand operatedxe2x80x9d systems in which one instrument was electrically connected (through a hierarchical switching network) to another through the intervention of a human operator who would physically plug one circuit into another. Such direct electrical connection of two or more channels between two points (at least one channel in each direction), a connection that provides a user with exclusive use of the channels to exchange information, is referred to as circuit switching, or line switching. Human operators have largely been replaced by systems which employ electronic switching systems (ESS), in which the instruments are automatically connected through the network by electronic systems.
Additionally, in many cases, the signalling system employs optical signalling instead of, or in addition to, electronic signalling. Switching systems that employ both optical and electronic signals are incapable of the achieving the operational speeds that an all-optical system might attain. That is, systems exist which, although they employ optical signals for data transmission, convert the optical signals to electronic signals for switching purposes, then convert the switched electronic signals back to optical signals for further transmission. One of the difficulties associated with all-optical telecommunications systems is the discovery of port binding information. That is, an optical network element (NE) such as an all-optical switch, may not be aware of the port to port connectivity between itself and other optical NEs within a telecommunications system. It would be highly desirable if this port-to-port connectivity information, or port binding information, could be automatically discovered without requiring the conversion of optical signalling to electronic signalling.
In an optical telecommunications network in accordance with the principles of the present invention, a link connection undergoes an automatic port recognition process, whereby the port binding information for the link is detected, recorded and shared with the network elements connected by the link, before the link is used to transmit bearer traffic. One of a group of optical network elements that communicate through an out of band channel, such as a LAN, is xe2x80x9celectedxe2x80x9d an NE leader. After election, the leader NE coordinates the port discovery process; requests for port xe2x80x9crecognitionxe2x80x9d, responses to requests, and other messages are passed through the NE leader on the out of band channel from one non-leader NE to another. Once the recognition process is set up through the leader NE, an optical test signal is transmitted along the link in question from the recognition requesting NE to all other NEs in the network. The optical test signal could be light of a frequency set aside for test purposes, or it may be light commonly used for data communication. In the context of the test the presence of any optical signal may be interpreted as the test signal. The receiving NEs monitor the power level at each of their xe2x80x9cinactivexe2x80x9d ports and the inactive port at which an increased energy level is detected is determined to be the port attached to the link in question. One advantage of using an optical signal and measuring received power at receiving ports in accordance with the principles of the present invention is that there is no need for converting optical signals to electrical signals, then interpreting the electrical signals. Thus, the operational speed of an NE may be maintained and the complexity and concomitant costs associated with port discovery may be minimized.
Each optical network element within the system includes a link status table and a recognition request queue. An NE employs the link status table to determine which of its ports have been xe2x80x9crecognizedxe2x80x9d, that is, which links have had their port binding information discovered. The NE performs the link recognition process on those links that have not been recognized. The NE leader places received recognition requests in a request queue and processes those requests as they make their way to the front of the queue. If the queue is a first in first out queue (FIFO queue), the requests are processed in the order in which they are received, but other prioritization schemes are possible. Through the link status table, each optical NE, such as an optical switching system, can select the link connections having a link recognition status indicating that the link is xe2x80x9cunrecognizedxe2x80x9d, then perform the recognition process for the related link connections.